Gothic Blue vs Phthalo Cyanine Blue

How close are they?

ΔE 8.8, close: similar, with a visible difference side by side. Phthalo Cyanine Blue is more muted than Gothic Blue.

Can I use Phthalo Cyanine Blue instead of Gothic Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Phthalo Cyanine Blue is more muted than Gothic Blue.

Can I use Gothic Blue instead of Phthalo Cyanine Blue?

The same difference applies the other way round: Gothic Blue is more saturated.

ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.